1. Field of the Invention
This invention relates to the field of hard disk drive suspensions having dual stage actuators. More particularly, this invention relates to the field of a dual stage actuator suspension for a hard disk drive, the suspension having a single microactuator device and employing pseudo symmetry to balance the suspension.
2. Description of Related Art
In a hard disk drive, the suspension is the component that holds the read-write head over the desired data track on the spinning magnetic hard drive. The disk drive could also be an optical disk or possibly other data storage technologies. As track densities increase and drives are made smaller, there is a constant need in the industry for greater precision in the disk drive components including the actuator(s) that move the read-write head to the correct data track.
Suspensions have been proposed that have dual stage actuators (DSAs), with the first stage being the voice coil motor that traditionally has moved the suspension, and the second stage being a microactuator mounted on the suspension itself that makes extremely fine adjustments to the head position. The system that positions the head, using either the voice coil motor in a traditional single actuator suspension, or a combination of the voice coil motor and the microactuator in a DSA suspension, is called the head positioning servo-system. The microactuator typically comprises a pair of piezoelectric devices such as lead zirconate titanate (PZT) devices mounted in a push-pull configuration, such that one PZT pulls one side of the suspension while the other PZT pushes the other side. For purposes of the present disclosure and for purposes of simplicity of discussion, the microactuator will generally be referred to as a PZT although it will be understood that microactuators other than PZTs can be used. Representative of a dual PZT type DSA suspension are U.S. Pat. No. 6,614,627 issued to Shimizu et al, and U.S. Pat. No. 6,731,472 issued to Okamoto et al, which describe DSA suspensions using PZT devices as the microactuators. Those patents employ two non-split PZTs. A non-split PZT, also called a single pole PZT, is a PZT which has only a single electrical pole per face. FIG. 1 is a representative illustration of a DSA type suspension 5 having two single-pole PZTs 8 and 9 according to the prior art.
Another known design uses a split PZT. A split PZT is a single device in which the device is split into two portions that can be driven separately, such that a single device is capable of both expanding on one side and contracting on the other side. Split PZTs are typically formed by metalizing both the top face and the bottom face of the device, with a split line in the middle created by photo patterning. A split PZT behaves as if it is two separate PZTs. Split PZTs typically have three electrical connections: a right side driving voltage connection, a left side driving voltage connection, and a common ground connection.
Other configurations of PZT microactuated suspensions have been proposed. U.S. Pat. No. 6,381,104 issued to Soeno et al. shows a piezoelectric moving-slider microactuator that moves the slider by rotation. U.S. Pat. No. 7,382,583 issued to Hirano et al. describes a DSA suspension that uses a rotary piezoelectric microactuator.
DSA suspensions that use a microactuator other than a PZT microactuator have also been proposed. U.S. Pat. Nos. 5,959,808 issued to Fan et al. and 5,995,334 issued to Fan et al. describe electrostatic microactuators for suspensions.
DSA suspensions have also been proposed using PZTs in various locations, including on the mount plate, on the load beam, or on the gimbal tongue close to the slider.
Due to the additional cost of DSA suspensions over traditional suspensions, it is believed that DSA suspensions have only been recently become available commercially. There is therefore a need for reducing manufacturing costs of DSA suspensions.